Sensory Receptors
Molecules of various materials are dispersed (spread) throughout the air we breathe. A special olfactory epithelium is located in the upper recesses of the nasal chambers in the head. Special hair cells in the olfactory epithelium are called chemoreceptors, because they receive these molecules in the air.

Olfactory Sensory Pathway
The information received by the olfactory hair cells is transmitted by way of the olfactory nerves (cranial nerves I). It passes through these nerves to the olfactory bulbs and then into the opposite cerebral hemisphere. Here, the information becomes the sensation of smell.